This invention relates to a magnetostrictive transducer, particularly to a magnetostrictive transducer of improved configuration for use in an ultrasonic resonant vibrator, more particularly to an ultrasonic resonant vibrator in a surgical handpiece.
Apparatus incorporating an ultrasonic resonant vibrator is known in the art for surgical use, particularly for surgical handpieces comprising tools for fragmenting tissue. In such apparatus the required ultrasonic vibrations may be produced by magnetostrictive means transmitted through a connecting member to an appropriate tool.
A representative example of such an apparatus is disclosed in U.S. Pat. No. 4,223,676, the disclosure of which is incorporated herein by reference. In the apparatus disclosed in U.S. Pat. No. 4,223,676 the magnetostrictive transducer is a magnetostrictive stack composed of a nickel alloy sandwich such as is taught in U.S. Pat. No. RE 25,033. The said stack comprises a plurality of elongated strips of magnetostrictive material, i.e. nickel alloy, forming a laminated structure. The laminations are necessary to reduce adverse effects, e.g. energy loss, from eddy currents.
In a later improved design the laminated stack was made with a shallow curved profile for added rigidity.
In order to function properly, a laminated transducer preferably:
1. should be mechanically stiff; PA1 2. have minimum acoustic losses; and PA1 3. should be relatively easy to handle away from its operating environment.
The transducer described above has proved to be effective and highly serviceable in its use in surgical procedures. However, despite its good performance record, it still has certain disadvantages. For example, the flat laminated structure tends to overheat if the flow of coolant is reduced for any reason and such overheating may result in serious damage to the apparatus. Also the flat construction gives mechanical stiffness in only one plane. This lack of overall rigidity may result in mechanical damage due to mishandling and, if the laminations become separated or bent, the entire apparatus may be rendered useless.
It has now been found that the above disadvantages are overcome if the transducer is made in the form of a substantially rigid column comprising elongated strips arranged in the form of radially extending fins.